The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that ...The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic （MHD） equilibrium with reversed current density （RCD） profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.展开更多
Solutions of Grad-Shafranov （CS） equation with Reversed Current Density （RCD） profiles present mag- netic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that...Solutions of Grad-Shafranov （CS） equation with Reversed Current Density （RCD） profiles present mag- netic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that a typical cylindrical （large aspect-ratio） RCD equilibrium configuration perturbed by the magnetic field of a circular loop （simulating a divertor） is capable of generate magnetic islands, due to the poloidal symmetry break of the GS equilibrium solution.展开更多
A junction barrier Schottky （JBS） rectifier with an improved P-well on 4H-SiC is proposed to improve the VF-IR trade-off and the breakdown voltage. The reverse current density of the proposed JBS rectifier at 300 K ...A junction barrier Schottky （JBS） rectifier with an improved P-well on 4H-SiC is proposed to improve the VF-IR trade-off and the breakdown voltage. The reverse current density of the proposed JBS rectifier at 300 K and 800 V is about 3.3 × 10-s times that of the common JBS rectifier at no expense of the forward voltage drop. This is because the depletion layer thickness in the P-well region at the same reverse voltage is larger than in the P＋ grid, resulting in a lower spreading current and tunneling current. As a result, the breakdown voltage of the proposed JBS rectifier is over 1.6 kV, that is about 0.8 times more than that of the common JBS rectifier due to the uniform electric field. Although the series resistance of the proposed JBS rectifier is a little larger than that of the common JBS rectifier, the figure of merit （FOM） of the proposed JBS rectifier is about 2.9 times that of the common JBS rectifier. Based on simulating the values of susceptibility of the two JBS rectifiers to electrostatic discharge （ESD） in the human body model （HBM） circuits, the failure energy of the proposed JBS rectifier increases 17% compared with that of the common JBS rectifier.展开更多
基金State University of Campinas and CNPq (brazili anagency) for financial support
文摘The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic （MHD） equilibrium with reversed current density （RCD） profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.
文摘Solutions of Grad-Shafranov （CS） equation with Reversed Current Density （RCD） profiles present mag- netic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that a typical cylindrical （large aspect-ratio） RCD equilibrium configuration perturbed by the magnetic field of a circular loop （simulating a divertor） is capable of generate magnetic islands, due to the poloidal symmetry break of the GS equilibrium solution.
基金Project supported by the Program for New Century Excellent Talents in University,China(Grant No.NCET-10-0052)the Fundamental Research Funds for the Central Universities of China(Grant No.HEUCFT1008)
文摘A junction barrier Schottky （JBS） rectifier with an improved P-well on 4H-SiC is proposed to improve the VF-IR trade-off and the breakdown voltage. The reverse current density of the proposed JBS rectifier at 300 K and 800 V is about 3.3 × 10-s times that of the common JBS rectifier at no expense of the forward voltage drop. This is because the depletion layer thickness in the P-well region at the same reverse voltage is larger than in the P＋ grid, resulting in a lower spreading current and tunneling current. As a result, the breakdown voltage of the proposed JBS rectifier is over 1.6 kV, that is about 0.8 times more than that of the common JBS rectifier due to the uniform electric field. Although the series resistance of the proposed JBS rectifier is a little larger than that of the common JBS rectifier, the figure of merit （FOM） of the proposed JBS rectifier is about 2.9 times that of the common JBS rectifier. Based on simulating the values of susceptibility of the two JBS rectifiers to electrostatic discharge （ESD） in the human body model （HBM） circuits, the failure energy of the proposed JBS rectifier increases 17% compared with that of the common JBS rectifier.
